1. Field of the Invention
The present invention is related to measurement circuits for measuring metrics such as circuit environment variables, and more particularly to a dynamic logic metric measurement circuit.
2. Description of Related Art
Environmental measurement circuits are finding application in integrated circuits such as processor cores, in which it is useful to evaluate and/or monitor variation in circuit environment metrics such as temperature and supply voltage. Such variations can lead to substantial changes in circuit performance and may vary rapidly. Therefore, it is desirable to make real-time measurements without increasing power consumption significantly, and without requiring large circuit area.
Existing delay-based measurement circuits typically employ a chain of static logic inverters in a delay line or ring-oscillator arrangement. The delay of the delay line is sensitive to one or more environment metrics and either the delay of the delay line or the frequency of the ring oscillator is measured to determine the value of the environment metric(s). However, frequency measurement places a limitation on the real-time (cycle-by-cycle) availability of the measurement data, as the frequency must be measured long enough to attain a desired resolution, and a typical static inverter chain delay measurement must be decoded to determine the length of the delay. Control logic and calibration/reference circuits are also typically needed in present environmental monitors so that the delay can be strongly correlated to the environmental metric that is being measured.
Therefore, it would be desirable to provide a metric measurement circuit requiring low power, small circuit area and does not require additional circuitry to decode the output. It would further be desirable to provide a metric measurement circuit that is self-referenced with respect to variations of non-measured circuit metrics.